Fixes #111 - corrects elseif to else in POSIX platform build support

source/buildsupport/POSIX/OpENer_PLATFORM_INCLUDES.cmake

@@ -5,7 +5,7 @@ macro(opener_platform_spec)
   get_property(languages GLOBAL PROPERTY ENABLED_LANGUAGES)
   if ("CXX" IN_LIST languages)
   	add_definitions(-DRESTRICT=)
-  elseif()
+  else()
   	add_definitions(-DRESTRICT=restrict)
   endif()
-endmacro(opener_platform_spec)
+endmacro(opener_platform_spec)